The war in Iran and the blockade of the Strait of Hormuz are set to dominate the Manila meetings attended by US Secretary of State Marco Rubio, Russian Foreign Minister Sergei Lavrov and top officials from Australia, Britain, China, the European Union, India, Japan and others.
The conflict is a key concern for the 11-nation Association of Southeast Asian Nations, which has a combined gross domestic product of about $US3.8 trillion heavily reliant on Middle East oil, exposing it to fallout that has stoked global inflation.
"We convene against the backdrop of profound geopolitical and geo-economic uncertainty," Maria Theresa Lazaro, the foreign secretary of the Philippines, which is chairing the grouping, said in opening remarks on Thursday.
"These issues transcend borders and underscore the reality that no nation can address today's complex security environment alone."
The US military completed a 12th successive night of attacks on Iran on Wednesday, with Iranian-aligned Houthis claiming hits the following day on two Saudi oil tankers, in a blockade that threatens a second chokehold on global oil supplies in the Red Sea, alongside the Strait of Hormuz.
The world has entered a "new period of turbulence and transformation", Chinese Vice-Foreign Minister Hua Chunying told a meeting of officials from ASEAN, China, Japan and South Korea on Thursday, warning of an urgent need for peace and stability.
A day earlier Rubio said the United States wanted a diplomatic solution in the Middle East, but Tehran was not playing ball.
Rubio held talks with Lavrov on Thursday for just under an hour, ranging over the Ukraine war and normalisation of US-Russia ties, Russia's foreign ministry said.
Lavrov "reaffirmed Russia's readiness for a political and diplomatic settlement of the conflict", it said, and told Rubio that Moscow remained committed to proposals put forward by the leaders of both nations.
In a one-paragraph statement, the US State Department said bilateral relations and "the need to end the Russia-Ukraine war" figured in the discussions.
Another focal point of talks in Manila has been the South China Sea and long-running tension between Beijing and US ally the Philippines, which Washington is treaty-bound to defend in the event of an attack on its vessels.
China's coast guard engaged in a brief altercation with Philippine navy personnel on Monday near a disputed reef in Manila's exclusive economic zone, prompting the countries to summon each other's ambassadors.
In a second incident on Thursday, China's coast guard accused the Philippines of "provocative actions" and said it had thwarted an intrusion at another disputed feature, the Scarborough Shoal.
The Philippine coast guard said water cannon was used on a government fisheries vessel that engaged in a "purely humanitarian undertaking".
China's Foreign Minister Wang Yi did not attend Thursday's forum in Manila and was due to join a regional meeting in Kyrgyzstan.
He told ASEAN counterparts on Wednesday the South China Sea was "our common home", where peace and stability rested in the hands of all.
Regional countries should "resist the incitement of foreign forces, oppose individual countries using the sea to make trouble," an official statement quoted him as saying.
